Deck 14: Streams and Floods: the Geology of Running Water

Question 1

The primary stream fed by tributaries within a drainage basin is termed a ____________.

A) lead stream
B) trunk stream
C) taproot stream
D) pirate stream

Answer 1

B

Question 2

How would the competency of an arid versus a temperate-region stream vary,in a downstream direction?

A) It would increase more in an arid-region stream.
B) It would increase less in an arid-region stream.
C) It would probably be the same.

Answer 2

A

Question 3

In uniform sediments with a relatively constant slope at the surface,a ____________ drainage network is expected.

A) dendritic
B) radial
C) rectangular
D) trellis

Answer 3

A

Question 4

The discharge of a river traveling through a humid region will typically ____________ downstream; the discharge of a river traveling through an arid region will typically ____________ downstream.

A) increase; increase
B) decrease; decrease
C) increase; decrease
D) decrease; increase

Question 5

In a region characterized by a parallel series of ridges and valleys,a ____________ drainage network is expected.

A) dendritic
B) radial
C) rectangular
D) trellis

Question 6

With time,a river may erode terrain to produce a low-lying plain termed a(n)____________.

A) astral plain
B) antedeluvial plain
C) peneplain
D) plateau

Question 7

Which sediment load carries electrically charged ions?

A) bed load
B) dissolved load
C) suspended load
D) bank load

Question 8

The deepest part of a mature river channel is where the water usually flows the fastest.

Question 9

Which two of these factors set the stage for the 1889 Johnstown flood?

A) poor design and "cutting corners" during construction
B) "cutting corners" during construction and heavy sedimentation filling in behind the dam
C) poor design and heavy sedimentation filling in behind the dam
D) poor design and obstruction of the spillway with debris

Question 10

Although the Nile River is longer,the Amazon River has the greatest discharge of any stream on Earth.

Question 11

Which three geologic terms are used to describe the course of an ephemeral stream?

A) arroyo; gulley; canyon
B) gulley; ditch; wadi
C) wash; gulley; arroyo
D) wash; arroyo; wadi

Question 12

All flowing water on the continents' surfaces is confined to stream channels.

Question 13

Which has greater competence?

A) a small, steep mountain stream
B) a broad, slow-flowing river

Question 14

In the region immediately surrounding an isolated volcano,a ____________ drainage network is expected.

A) dendritic
B) radial
C) rectangular
D) trellis

Question 15

All the water in rivers and streams arrives directly from rainfall runoff.

Question 16

The sediment load of a stream consists of only those grains that are fine enough to stay in suspension.

Question 17

Ephemeral streams ____________.

A) consist of a series of intertwined channels that are overloaded with sediment
B) have flowing water either episodically or during a portion of the year
C) have a channel that is highly sinuous (curvy)
D) divert flow from streams they have intersected through stream erosion.

Question 18

As the velocity of flow decreases,____________.

A) flow tends to become more laminar
B) the maximum flow velocity decreases
C) suspended sediment starts to be deposited
D) All of the above are correct.

Question 19

Which sediment load is likely to move the least,in between periods of flood?

A) bed load
B) dissolved load
C) suspended load
D) bank load

Question 20

In a region with prominent orthogonal sets of joints,a ____________ drainage network is expected.

A) dendritic
B) radial
C) rectangular
D) trellis

Question 21

Moving downstream,the flow of a stream or river usually becomes less ____________.

A) turbulent
B) saline
C) meandering
D) laminar

Question 22

The stream gradient of most rivers ____________.

A) is greater near the source than near the mouth
B) is greater near the mouth than near the source
C) does not change significantly as the river flows downstream
D) is greater for a meandering stream than for any other type

Question 23

The inner edge of a meander,where sediment is deposited,is a(n)____________.

A) meander neck
B) cut bank
C) point bar
D) abandoned meander

Question 24

The shape of a delta is primarily determined by ____________.

A) the shape of the river channel near the mouth
B) the average grain size of the suspended and bed loads
C) whether river currents, wave-driven currents, or tidal currents are locally predominant
D) the type of rock that is weathering at outcrop near the headwaters of the river

Question 25

The flat-lying area surrounding a river channel is termed the ____________.

A) base level
B) floodplain
C) stream gradient
D) thalweg

Question 26

Within a meander,where is sediment most likely to be deposited?

A) on the outer bank (cut bank) of the meander
B) on the inner bank (point bar) of the meander
C) uniformly to either side of the meander

Question 27

The lowest elevation to which a stream can downcut is the ____________.

A) base level
B) floodplain
C) stream gradient
D) thalweg

Question 28

All else being equal,water will flow faster in a stream that has a ____________.

A) steep stream gradient
B) gentle stream gradient

Question 29

Which has greater capacity?

A) a small, steep mountain stream
B) a broad, slow-flowing river

Question 30

The base level of a tributary would become ____________ if a dam and reservoir were constructed where it flowed into a trunk stream.

A) lower
B) slower
C) faster
D) higher

Question 31

A river flowing through a region of horizontally bedded sedimentary rock cuts downward from a shale into a quartz sandstone after being rejuvenated by regional uplift.What difference would you see in the sediment load of the river?

A) increased rock fragment content
B) increased black sand content
C) increased quartz sand content
D) increased dissolved mineral (ion) content

Question 32

The slope of a stream surface measured between two points along its course is the ____________.

A) base level
B) floodplain
C) gradient
D) thalweg

Question 33

The distinction between a valley and a canyon is ____________.

A) nonexistent; the two terms are synonymous
B) that the sides of a canyon are steeper than those of a valley
C) that the sides of a valley are steeper than those of a canyon
D) that valleys are often cut by streams; canyons are eroded out by the wind

Question 34

At a waterfall,where two sedimentary lithologies are juxtaposed,which lithology is generally more likely to form a cliff over which the water falls?

A) sandstone
B) shale

Question 35

Meandering streams ____________.

A) consist of a series of intertwined channels that are overloaded with sediment
B) have flowing water either episodically or during a portion of the year
C) have a channel that is highly sinuous (curvy)
D) are those that divert flow from streams they have intersected through stream erosion

Question 36

Look at river Deltas A and B and choose the correct statement about the river sediment loads and coastal processes that might be destroying the deltas.

A) Delta A receives more river sediment and is being destroyed more quickly by coastal processes.
B) Delta B receives more river sediment and is being destroyed more quickly by coastal processes.
C) Delta A receives more river sediment and is being destroyed less quickly by coastal processes.
D) Delta B receives more river sediment and is being destroyed less quickly by coastal processes.

Question 37

The outer edge of a meander,where material is being eroded,is a(n)____________.

A) meander neck
B) cut bank
C) point bar
D) abandoned meander

Question 38

Ultimately,the base level of a stream valley can be no lower than ____________.

A) the average elevation of the continent on which it is found
B) the level of water in the world's oceans
C) the average depths of the world's ocean basins

Question 39

All else being equal,water will flow faster in a stream with ____________.

A) well-developed meanders
B) a straight channel

Question 40

Braided streams ____________.

A) consist of a series of intertwined channels that are overloaded with sediment
B) have flowing water either episodically or during a portion of the year
C) have a channel that is highly sinuous (curvy)
D) are antecedent with respect to geologic structures

Question 41

Geological evidence suggests that many millions of years ago,the Amazon flowed toward the west rather than the east.

Question 42

If the tributaries of the Mississippi River were to erode northeastward and reach Lake Michigan (which happened in the past),what would be the effect on the size of the Atlantic Ocean drainage basin shown in the figure below?

A) It would not change.
B) It would become smaller.
C) It would become larger.
D) It is not possible to determine from the information given.

Question 43

The deltas of all major rivers consist of multiple radiating lobes of sediment in a "bird's foot" configuration,similar to the Mississippi River Delta.

Question 44

In areas that have become urbanized,the percolation of rainwaters tends to decrease and the speed at which rainwaters flow into streams and rivers tends to increase.Which of the following would be good ways to counteract this effect?

A) Dig drainage ditches to the streams and rivers, for rainwaters to flow through quickly.
B) Dig out shallow areas for rainwater runoff to collect into, to allow slow percolation into soils.
C) Increase the carrying capacity of storm water sewer systems.
D) Both A and C

Question 45

A 100-year flood is more catastrophic than a 50-year flood.

Question 46

All flooding events occur so rapidly that there is no time to alert people in harm's way.

Question 47

If you were studying the sediments along the beach and narrow continental shelf here,how could you tell that the river once flowed from the volcanoes straight out to the coast,instead of flowing somewhere inland as it does now?

A) Look for mineral and rock clasts of volcanic origin in the newest sediments of the beach and continental shelf
B) Look for volcanic ash
C) Look for mineral and rock clasts of volcanic origin in the older sediments of the beach and continental shelf
D) Both a and b are correct.

Question 48

At a delta,____________.

A) stream gradient decreases
B) a single channel breaks into multiple, radiating distributary channels
C) a and b are both correct.
D) None of the above are correct.

Question 49

The potential abrupt change of primary discharge of water from the Mississippi River to the Atchafalaya River would be an example of__________?

A) superposition
B) laminar flow
C) antecedence
D) piracy

Question 50

Pirate streams ____________.

A) consist of a series of intertwined channels that are overloaded with sediment
B) have flowing water either episodically or during a portion of the year
C) have a channel that is highly sinuous (curvy)
D) have increased their drainage areas

Question 51

V-shaped stream valleys result from the downcutting of stream erosion and ____________.

A) mass wasting on the valley sides
B) isostatic rebound
C) the "rule of the V's"
D) conservation of angular momentum

Question 52

If a 50-year flood occurs on the Mississippi River in 2010,what is the probability that a flood of the same magnitude will occur in 2011?

A) zero
B) 1%
C) 2%
D) 50%

Question 53

Flood recurrence and probability graphs like the one shown below rely on historic records.The predictions for severe floods on graphs like this one are supported by few data points because data for such graphs have generally not been collected longer than a century.What effect would urbanization have on the reliability of using this kind of graph to calculate the frequency and severity of major floods?

A) an underestimation of severe flood hazard
B) an overestimation of severe flood hazard
C) Urbanization would probably not affect the reliability of estimating severe flood hazard using this graphic predictive technique.

Question 54

If a stream cuts through flat-lying sediments to reach an anticline produced in an ancient orogenic event,the course of the stream will likely be unaffected.

Question 55

The construction of dams on major rivers often has both positive and negative effects.Which of the following would not be a negative effect of damming rivers?

A) erosion and loss of beaches over time
B) destruction and retreat of delta shorelines
C) decrease in replenishment of silt to floodplains after periods of prolonged heavy rainfall
D) lower turbidity in river water

Question 56

A meander that is cut off to become completely isolated from the main channel,but that retains water,is a(n)____________.

A) meander neck
B) cut bank
C) oxbow lake
D) abandoned meander